When did you conceive if your due date is october 4th?

To calculate the approximate conception date, we need to count back from the due date. Pregnancy typically lasts about 40 weeks or 280 days from the first day of the last menstrual period (LMP).

Counting backward 40 weeks from October 4th:

October 4th - 40 weeks = December 20th

So the approximate conception date is around December 20th.